Technical Field
The present invention relates to ultrasonic diagnosis in which ultrasound is transmitted to and from a subject and an ultrasonic tomographic image is obtained, and in particular, to an image process of a tomographic image of a blood vessel.
Background Art
Properties of plaques attached to an inner surface of a blood vessel wall observed in arteriosclerosis or the like may be classified primarily into four types, including fibrous, calcified, fatty, and bleeding. The fibrous and calcified plaques are called stable plaques, because these plaques tend not to separate from the blood vessel wall and are stable. On the other hand, the fatty and bleeding plaques are called unstable or movable plaques, because these plaques tend to separate from the blood vessel wall and tend to be unstable. Unstable plaque is given a movement by a pressure such as bloodstream, and, at a certain point, is separated from the blood vessel wall. When the plaque is separated from the blood vessel wall, a sequence of pathoses is caused, including formation of a thrombus, narrowing of the internal cavity of the blood vessel, and closure of the blood vessel, resulting in cerebral infarction and myocardial infarction.
In some cases, there is a portion in a part of the unstable plaque that sways according to a change of a bloodstream due to the heartbeat. For example, this portion moves up and down in a floating manner, or moves in a movement similar to an expansion and contraction movement of a jellyfish in response to the bloodstream. The former is called a floating plaque and the latter is called a jellyfish sign. In the following description, the swaying portion of the unstable plaque which is further unstable will be called a “free-moving piece”. The free-moving piece is a part which may be separated from the blood vessel wall in the near future, which may be detached from the plaque body, and which may form a thrombus.
Diagnosis of the plaque by an ultrasonic diagnosis device has advantages; for example the property of the plaque can be classified by the brightness (intensity) of the echo, resolution is high, and the method is superior in real time diagnosis. JP 2009-148395 A discloses diagnosis of plaques using an ultrasonic tomographic image.
When the movement of the free-moving piece is to be observed in the ultrasonic tomographic image of the related art, recognizing the movement is difficult, because the movement is not so significant and is mixed in the movement of the blood vessel wall by the heartbeat.
An advantage of the present invention is that the free-moving piece is extracted and information on the position of the free-moving piece is provided.